Study on the low frequency instability in the near wake of a circular disk

Based on data of LES (large eddy simulation) and hot wire anemometry, the low frequency instability in the near wake of a circular disk at Re=104 was studied by wavelet analysis and FFT method. It is found that, besides Kelvin-Helmholtz frequency StKH≈16 and vortex shedding frequency StV≈014, there are two low frequencies, namely StL1≈002 and StL2≈003. Further study shows that the two frequencies are correlated with the azimuthal motion of the vortex shedding location and the pumping motion of the recirculation region, respectively. The study presents a reasonable explanation of the scattering in the value of the low frequency in the near wake of the bluff body.